1. Field of the Invention
The present invention relates to monolithic structures with integrated optical waveguide and mirror.
The expression "monolithic structure" designates a structure using a technology common to the production of various elements and not to a technique for assembling different components produced separately.
In the text of the present invention, the expression "optical waveguide" covers structures capable of guiding light passively as well as those capable of guiding light with amplification of the optical wave.
The present invention is applicable in particular to the field of optical telecommunications.
2. Background Information
A structure with integrated optical waveguide and mirror is described in document FR-A-2 655 775. More particularly, this document proposes producing a waveguide-photodetector structure by epitaxing on a flat substrate, various layers of materials needed to produce an optical waveguide and photodetector. The different epitaxed layers are then attacked either chemically or by some other means in order to form a mirror capable of reflecting light from the waveguide towards the photodetector.
FIG. 1 shows a waveguide-photodetector structure produced by a prior art process, such as that described in document FR-A-2 655 775. FIG. 1 shows a substrate 100, on which the following layers have been successively epitaxed: a lower confinement layer 110, a waveguide forming layer 120, an upper confinement layer 130, and a photodetective layer 140 which comprises a photodiode 150. The inclined mirror-forming plane 160 is produced by chemically attacking the different epitaxed layers 110, 120, 130 and 140 and reflects light from the optical waveguide-forming layer 120 towards the photodiode junction 150.
While the process used to obtain the structure with integrated optical waveguide and mirror proposed in document FR-A-2 655 775 constitutes a notable improvement over earlier proposed processes, comprising notably only a single epitaxy step, the structure nevertheless has the drawback of being costly and delicate to fabricate since the inclined mirror-forming plane 160 is produced with the aid of a succession of selective, and therefore different, chemical etches of epitaxial layers 110, 120, 130 and 140.
The salient edge 165 of the mirror 160 of the structure with integrated optical waveguide and mirror obtained by the process has also been found to be particularly fragile.